U.S. patent number 9,445,455 [Application Number 14/574,057] was granted by the patent office on 2016-09-13 for communication apparatus and communication method.
This patent grant is currently assigned to Panasonic Corporation. The grantee listed for this patent is Panasonic Corporation. Invention is credited to Junichi Morita.
United States Patent |
9,445,455 |
Morita |
September 13, 2016 |
Communication apparatus and communication method
Abstract
A communication apparatus includes: a first communicator that
communicates with another communication apparatus through a first
communication path; a second communicator that communicates with
the other communication apparatus through a second communication
path; a communication-path monitor that monitors a condition of a
communication through the first communicator; a
switching-setup-packet generator that sequentially generates
switching-setup packets to be transmitted through the first and
second communicators, based on a determination indicating that the
condition of the communication through the first communicator is
bad; and a switching controller that switches between
communications through the first and second communicators, based on
a type of which response data for the switching-setup packets
arrive from the other communication apparatus and an order in which
response data for the switching setup packets arrive from the other
communication apparatus.
Inventors: |
Morita; Junichi (Tokyo,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Corporation |
Osaka |
N/A |
JP |
|
|
Assignee: |
Panasonic Corporation (Osaka,
JP)
|
Family
ID: |
53483529 |
Appl.
No.: |
14/574,057 |
Filed: |
December 17, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20150189545 A1 |
Jul 2, 2015 |
|
Foreign Application Priority Data
|
|
|
|
|
Dec 27, 2013 [JP] |
|
|
2013-273112 |
Sep 17, 2014 [JP] |
|
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2014-188960 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
76/15 (20180201); H04W 88/06 (20130101); H04W
84/12 (20130101) |
Current International
Class: |
H04W
28/02 (20090101); H04W 88/06 (20090101); H04W
40/12 (20090101); H04W 76/04 (20090101); H04W
76/02 (20090101); H04W 84/12 (20090101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
IEEE Computer Society "Part11:Wireless LAN Medium Access
Control(MAC)and Physical Layer(PHY) Specifications
Amendment3:Enhancements for Very High Throughput in the 60 GHz
Band" IEEE Std 802.11ad,Dec. 28, 2012, pp. 396-407. cited by
applicant.
|
Primary Examiner: Elallam; Ahmed
Attorney, Agent or Firm: Seed IP Law Group PLLC
Claims
What is claimed is:
1. A communication apparatus, comprising: a first communicator that
communicates with another communication apparatus through a first
communication path; a second communicator that communicates with
the other communication apparatus through a second communication
path; a communication-path monitor that monitors a condition of a
communication through the first communicator; a
switching-setup-packet generator that sequentially generates
switching-setup packets to be transmitted through the first
communicator and the second communicator, when packet loss occurs
in the communication through the first communicator; and a
switching controller that controls a switching control between the
communication through the first communicator and a communication
through the second communicator, based on a type of which response
data for the switching-setup packets arrive from the other
communication apparatus and an order in which the response data for
the switching setup packets arrive from the other communication
apparatus.
2. The communication apparatus according to claim 1, wherein the
first communicator communicates by using a frequency band of 60
GHz, and the second communicator communicates by using a frequency
band of 2.4 GHz or 5 GHz.
3. The communication apparatus according to claim 1, wherein the
switching controller uses Fast Session Transfer (FST) as a
switching protocol for switching between the communication through
the first communicator and the communication through the second
communicator.
4. The communication apparatus according to claim 3, wherein the
switching controller communicates a switching-control packet based
on the FST with the second communicator by using on-channel
tunneling (OCT).
5. The communication apparatus according to claim 1, wherein the
first communicator receives, from the other communication
apparatus, a first response packet for at least one of the
switching-setup packets, and when the first response packet
indicates a response for reception success, the switching
controller continues the switching control between the
communication through the first communicator and the communication
through the second communicator.
6. The communication apparatus according to claim 5, wherein, when
the second communicator receives, from the other communication
apparatus, a second response packet for at least one of the
switching-setup packets after receiving the first response packet,
the switching controller omits transmission control for the second
response packet.
7. The communication apparatus according to claim 1, wherein the
first communicator receives, from the other communication
apparatus, a first response packet for at least one of the
switching-setup packets, and when the first response packet
indicates a reject response, the switching controller omits
transmission control for the first response packet; and after
receiving the first response packet that indicates a reject
response, the second communicator receives, from the other
communication apparatus, a second response packet for at least one
of the switching-setup packets, and when the second response packet
indicates a response for reception success, the switching
controller continues the switching control.
8. The communication apparatus according to claim 1, wherein the
second communicator receives, from the other communication
apparatus, a second response packet for at least one of the
switching-setup packets, and when the second response packet
indicates a response for reception success, the switching
controller continues the switching control.
9. The communication apparatus according to claim 8, wherein the
first communicator transmits, to the other communication apparatus,
a session-disconnect packet for disconnecting a communication
session, and the switching controller suspends to switch the
communication through the first communicator.
10. The communication apparatus according to claim 1, wherein the
second communicator receives, from the other communication
apparatus, a second response packet for at least one of the
switching-setup packets; and when the switching controller
determines that the second response packet indicates a reject
response, the first communicator transmits a session-disconnect
packet, and the switching controller suspends to switch
communication through the first communicator, and the second
communicator re-transmits a switching-setup packet, and the
switching controller continues the switching control according to a
response for reception success of the re-transmitted
switching-setup packet.
11. A communication method for a communication apparatus, the
method comprising: communicating with another communication
apparatus through a first communicator; communicating with the
other communication apparatus through a second communicator;
monitoring a condition of a communication through the first
communicator; sequentially generating switching-setup packets to be
transmitted through the first communicator and the second
communicator, when the communication through the first communicator
is a bad condition; and controlling a switching control between the
communication through the first communicator and a communication
through the second communicator, based on a type of which response
data for the switching-setup packets arrive from the other
communication apparatus and an order in which the response data for
the switching setup packets arrive from the other communication
apparatus.
Description
The present application is based on and claims the benefit of
Japanese Patent Application No. 2013-273112 filed in the Japan
Patent Office on Dec. 27, 2013 and Japanese Patent Application No.
2014-188960 filed in the Japan Patent Office on Sep. 17, 2014, the
entire contents of which are incorporated herein by reference.
BACKGROUND
1. Technical Field
The present disclosure relates to a communication apparatus and a
communication method. For example, the present disclosure relates
to a communication apparatus that performs communication by using a
plurality of communication paths.
2. Description of the Related Art
Nowadays, with the increasing functionality of mobile terminals and
the increasing densities of video content, video files with high
image qualities and large-size files are also increasingly
transmitted and received by mobile terminals. In such an
environment, a communication terminal is generally required to
transmit/receive (communicate) a large-size file to/from another
party's communication terminal at high speed.
Short-range wireless communication using a millimeter wave band
(hereinafter referred to as "millimeter wave communication") has
attracted attention as a method for high-speed communication.
Millimeter wave communication is a communication method that can
realize gigabit throughput or higher. For communication between
mobile terminals, millimeter wave communication is also expected to
play a role of replacing infrared communication or reducing traffic
in public communication networks.
In IEEE802.11ad (60 GHz), which is a Wireless Fidelity (WiFi)
standard for millimeter wave communication, Fast Session Transfer
(FST) has been standardized. FST is a system that performs seamless
switching on the order of milliseconds between a millimeter wave
communication and a wireless local area network (LAN) (5 GHz/2.4
GHz) communication (i.e., switching of a communication using 60 GHz
to a communication using 5 GHz/2.4 GHz or switching from a
communication using 5 GHz/2.4 GHz to a communication using 60 GHz).
FST has attracted attention as a standard for compensating for
high-speed communication, which is a feature of the millimeter wave
communication (see, for example, "Part 11: Wireless LAN Medium
Access Control (MAC) and Physical Layer (PHY) Specifications
Amendment 3: Enhancements for Very High Throughput in the 60 GHz
Band", IEEE Computer Society IEEE Std 802.11ad, Dec. 28, 2012,
P396-P407 (this document is referred to as "Non-Patent Document 1"
hereinafter).
As a system for transmitting a plurality of control packets between
two communication apparatuses, a communication system as described
below is known (see, for example, Japanese Unexamined Patent
Application Publication No. 2008-177754 (hereinafter referred to as
Patent Document 1)).
The communication system disclosed in Patent Document 1 has two
transmission paths between first and second terminal stations and a
base station. The two transmission paths are constituted by a
wireless communication path (a transmission path A) and a
communication path (a transmission path B) using a power line. By
using the two transmission paths, the first terminal station or the
second terminal station and the base station transmit data packets
therebetween in a downlink direction and transmit control packets
in an uplink direction. The downlink direction is a direction from
the base station to the first or second terminal station. The
uplink direction is a direction from the first or second terminal
stations to the base station.
Patent Document 1 discloses two transmission modes, that is, a
high-speed transmission mode and a high-quality transmission mode.
The high-speed transmission mode is a mode in which transmission
packets (data packets) are distributed to the two transmission
paths, and is used for transmission in the downlink direction. The
high-quality transmission mode is a mode in which even when the
quality of communication in one of the transmission paths is poor,
the other transmission path is used to complement the
communication. The high-quality transmission mode is mainly used in
the uplink direction.
In the technology disclosed in Patent Document 1 or Non-Patent
Document 1 do not sufficiently consider a communication situation
at 60 GHz for switching of the communication path. Consequently,
the accuracy of switching the communication path is
insufficient.
SUMMARY
One non-limiting and exemplary embodiment provides a communication
apparatus that can improve the accuracy of switching a
communication path.
A communication apparatus according to the present disclosure
includes: a first communicator that communicates with another
communication apparatus through a first communication path; a
second communicator that communicates with the other communication
apparatus through a second communication path; a communication-path
monitor that monitors a condition of a communication through the
first communicator; a switching-setup-packet generator that
sequentially generates switching-setup packets to be transmitted
through the first communicator and the second communicator, when
packet loss occurs in the communication through the first
communicator; and a switching controller that controls a switching
control between the communication through the first communicator
and a communication through the second communicator, based on a
type of which response data for the switching-setup packets arrive
from the other communication apparatus and an order in which the
response data for the switching setup packets arrive from the other
communication apparatus.
These general and specific aspects may be implemented using a
system, a method, and a computer program, and any combination of
systems, methods, and computer programs.
According to the present disclosure, it is possible to improve the
accuracy of switching a communication path.
DETAILED DESCRIPTION
FIG. 1 is a block diagram illustrating an example configuration of
a communication system according to an embodiment;
FIG. 2 is a flowchart illustrating an example operation of a
communication terminal (a transmission terminal);
FIG. 3 is a flowchart illustrating an operation example of a
communication terminal (a reception terminal);
FIG. 4 is a sequence diagram illustrating an operation example in a
first control pattern for the communication terminals in the
embodiment;
FIG. 5 is a sequence diagram illustrating an operation example in a
second control pattern for the communication terminals in the
embodiment;
FIG. 6 is a sequence diagram illustrating an operation example in a
third control pattern for the communication terminals in the
embodiment;
FIG. 7 is a sequence diagram illustrating an operation example in a
fourth control pattern for the communication terminals in the
embodiment;
FIG. 8 is a sequence diagram illustrating an operation for
switching the frequency band from 60 GHz to 5 GHz by using FST
defined in IEEE802.11ad;
FIG. 9 is a sequence diagram illustrating an operation for
switching the frequency band from 60 GHz to 5 GHz through FST using
OCT defined in IEEE802.11ad; and
FIG. 10 is a sequence diagram illustrating an operation that is
assumed to be performed during switching of the frequency band from
60 GHz to 5 GHz as a result of a bad condition of a communication
using 60 GHz.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the present disclosure will be described below
with reference to the accompanying drawings.
(Background that LED to Technology According to Present
Disclosure)
In order for millimeter wave communication to be in widespread use
in the future, it needs to coexist with wireless local area
networks (LANs) that are widely used today. For terminals (e.g.,
mobile terminals) having millimeter wave communication functions,
terminals having both a communication function for millimeter wave
communication and a communication function for wireless LAN
communication are thought to be widely used.
Compared with the currently available wireless LAN communication,
the millimeter wave communication has features in its short
communication distance and strong directivity, while having a
high-speed communication capability. That is, compared with the
currently available wireless LAN communication, the millimeter wave
communication is large in changes in throughput during
communication, and thus communication sessions are easily
disconnected. Thus, terminals that support millimeter wave
communication have a function for millimeter wave communication and
wireless LAN communication (e.g., a function for seamless switching
between the communications) to cooperate with each other during
communication.
FIG. 8 is a sequence diagram illustrating an operation for
switching the frequency band from 60 GHz to 5 GHz by using FST
defined in IEEE802.11ad. That is, FIG. 8 is a schematic diagram
illustrating a control sequence of FST defined in IEEE802.11ad,
which performs a switching between a communication path for
millimeter wave communication and a communication path for wireless
LAN communication. FST is a system used for seamless switching
control in milliseconds between a millimeter wave communication and
a wireless LAN communication. FIG. 8 is a control sequence for
switching from a communication path for millimeter wave
communication to a communication path for wireless LAN
communication, that is, for switching the frequency band from 60
GHz to 5 GHz. The switching control includes three steps: switching
setup, a switching process, and switching confirmation.
In FIG. 8, communication terminals 1 and 2 mutually exchange
switching-setup packets (S41) by using the frequency band (e.g., 60
GHz) from which the switching is to be performed (i.e., the
frequency band before the switching). The communication terminals 1
and 2 perform corresponding switching processes (S42), and then
exchange switching confirmation packets (S43) by using the
frequency band (e.g., 5 GHz) to which the switching is to be
performed (i.e., the frequency band after the switching). In the
switching processes, the communication path is switched. Each
switching-setup packet is a packet for requesting start of the
switching process. Each switching confirmation packet is a packet
for querying whether or not the switching process in the other
party's terminal is successfully completed.
For high-speed transfer between the communication terminals 1 and 2
that support both of the frequency bands of 60 GHz and 5 GHz, they
use 60 GHz, which allows higher speed communication, to communicate
with each other, and continue the communication by using 5 GHz upon
determining that the condition of the communication at 60 GHz
becomes bad. However, when the condition of the communication using
60 GHz is already bad at a timing at which the communication
terminals 1 and 2 determine that the frequency band is to be
switched (i.e., at a timing at which the switching-setup packets
are transmitted), it is difficult for the communication terminals 1
and 2 to exchange the switching-setup packets, and the switching
processes are not executed. Thus, the communication using 60 GHz
continues, and consequently, packet loss occurs. The switching of
the frequency band corresponds to switching of the communication
path.
For IEEE802.11ad, the communication terminals 1 and 2 may use
on-channel tunneling (OCT) as measures for a situation in which it
is difficult to perform frequency switching. OCT is one scheme on a
standard which uses, before a switching process, the frequency band
to which the switching is to be performed to exchange
switching-setup packets, instead of using the frequency band from
which the switching is to be performed.
FIG. 9 is a sequence diagram illustrating an operation for
switching the frequency band from 60 GHz to 5 GHz through FST using
OCT defined in IEEE802.11ad. That is, FIG. 9 is a schematic diagram
illustrating a sequence for a frequency band (communication path)
switching through FST utilizing OCT. In FIG. 8, the frequency band
(e.g., 60 GHz) from which the switching is to be performed is used
to exchange the switching-setup packets, as described above. In
FIG. 9, by utilizing OCT and using the frequency band (e.g., 5 GHz)
to which the switching is to be performed, a switching controller
15 (described below) exchanges the switching-setup packets (S51),
before the switching process. The switching processes (S52 and S53)
and subsequent processes in FIG. 9 are substantially the same as
the switching processes (S42 and S43) and the subsequent processes
in FIG. 8. By utilizing OCT, the switching controller 15 can use
the frequency band (e.g., 5 GHz) to which the switching is to be
performed, to perform packet exchange, before the switching
process.
FIG. 10 is a sequence diagram illustrating an operation that is
assumed to be performed during switching of the frequency band from
60 GHz to 5 GHz as a result of a bad condition of a communication
using 60 GHz. That is, FIG. 10 is a schematic diagram illustrating
a control sequence for switching a communication from 60 GHz to 5
GHz when the condition of the communication using 60 GHz becomes
bad. FIG. 10 illustrates a sequence based on FIGS. 8 and 9.
In FIG. 10, the communication terminal 1 transmits a
switching-setup packet to the communication terminal 2 (S61) by
using the frequency band (e.g., 60 GHz) from which the switching is
to be performed. However, the communication terminal 1 does not
receive, from the communication terminal 2, a response to the
switching-setup packet within a state transition timer (STT) period
(S62 and S63). Thus, before the switching process, the
communication terminal 1 uses OCT to re-transmit the
switching-setup packet to the communication terminal 2 (S64) by
using the frequency band (e.g., 5 GHz) to which the switching is to
be performed.
However, in FIG. 10, the communication terminal 1 adds a delay
corresponding to the STT period until it transmits the
switching-setup packet by using FST. Although the value of the STT
is not defined in IEEE802.11ad, the value of the STT in typical
implementations is a value in units of seconds. Consequently, it is
difficult to switch the communication path at high speed on the
order of milliseconds.
Accordingly, it is conceivable to transmit the switching-setup
packets in the same period of time or serially by using the
frequency band (60 GHz) from which the switching is to be performed
and the frequency band (5 GHz) to which the switching is to be
performed. For example, Patent Document 1 discloses a technology
for transmitting control packets including switching-setup packets
in the same period of time.
In Patent Document 1, the high-quality transmission mode
corresponds to the technology for transmitting control packets in
the same period of time, but Patent Document 1 discloses processing
for control packets in only one direction. That is, what is
described in Patent Document 1 is that, even when the communication
quality of one of the transmission paths A and B is bad, complement
is possible using the other transmission path A or B, since the
packets are transmitted through both the transmission path A and
the transmission path B in the same period of time. What is also
described is that, when packets are received through both of the
transmission paths A and B, both of the packets are combined or a
packet that has been received through the transmission path whose
communication quality is higher is selected.
However, no consideration has been given to bidirectional arrival
orders, that is, a first arrival order in which switching-setup
packets arrive at the communication terminal 2 and a second arrival
order in which response packets for the switching-setup packets
arrive at the communication terminal 2. Thus, even when the
technology disclosed in Patent Document 1 is applied to
communication path switching using FST, it is difficult to
appropriately switch the transmission path.
The description below is given of a communication apparatus and a
communication method that can improve the accuracy of switching a
communication path.
Embodiment
FIG. 1 is a block diagram illustrating an example configuration of
a communication system 100 and example configurations of
communication terminals 10 and 20 in an embodiment. The
communication system 100 includes the communication terminals 10
and 20. The communication terminal 10 and the communication
terminal 20 are connected to each other through communication paths
30. The communication paths 30 include, for example, a first
communication path 31 and a second communication path 32. The
number of communication paths included in the communication paths
30 may be three or more.
The communication terminals 10 and 20 are applied to, for example,
communication terminals that transfer files or that perform data
streaming. The communication terminals 10 and 20 are, for example,
mobile phones, smartphones, personal computers (PCs), or tablet
terminals. The communication terminals 10 and 20 may also be
communication apparatuses (e.g., communication servers) other than
such communication terminals.
Communication signals that comply with a millimeter wave
communication system or another communication system are
transmitted through the first communication path 31. Communication
signals that comply with a wireless LAN communication system or
another communication system are transmitted through the second
communication path 32. As long as communication signals whose
communication characteristics are variable more easily than those
of communication signals transmitted through the second
communication path 32 are transmitted through the first
communication path 31, the frequency bands used for communication
are not particularly limited. The millimeter wave communication
uses, for example, a frequency band of 60 GHz. The wireless LAN
communication complies with, for example, the IEEE802.11n standard
and uses a frequency band of 5 GHz or 2.4 GHz.
In the first communication path 31, for example, the maximum
throughput is on the order of gigabits (e.g., 2 Gbps), but
communication is easily interrupted. In the second communication
path 32, communication at about 100 Mbps can be performed
stably.
The communication terminal 10 includes a first communicator 11, a
second communicator 12, a switching-control-packet generator 13, a
switching-setup-packet generator 14, the switching controller 15
noted above, and a communication-path monitor 16.
The first communicator 11 communicates data with the communication
terminal 20 through the first communication path 31. The second
communicator 12 communicates data with the communication terminal
20 through the second communication path 32.
The switching-control-packet generator 13 generates a
switching-control packet for switching a communication path from
the first communication path 31 to the second communication path 32
or from the second communication path 32 to the first communication
path 31. The switching of the communication path from the first
communication path 31 to the second communication path 32
corresponds to switching of the communicator from the first
communicator 11 to the second communicator 12. The switching of the
communication path from the second communication path 32 to the
first communication path 31 corresponds to switching of the
communicator from the second communicator 12 to the first
communicator 11. The switching controller 15 handles protocols
including, for example, FST.
Examples of the switching-control packets include a switching-setup
packet, a response packet for a switching-setup packet, a,
switching confirmation packet, an acknowledgement response packet
for a switching confirmation packet, and a session-disconnect
packet. The session-disconnect packet is a packet for requesting
disconnection of a communication session. The
switching-setup-packet generator 14 generates the switching-setup
packet.
In order to switch communication path in accordance with a
determination made by the communication-path monitor 16, the
switching-setup-packet generator 14 generates switching-setup
packets sequentially (e.g., continuously, at substantially the same
time (in the same period of time), or within a predetermined time)
through each of the first communicator 11 and the second
communicator 12. The "substantially the same time" refers to a
state in the transmission times of the switching-setup packets
partly overlap each other.
For example, when the communication-path monitor 16 determines that
the condition of the first communication path 31 is bad on the
basis of FST, the switching controller 15 controls switching of the
communication path (the communicator) on the basis of a first
arrival order and a second arrival order. The first arrival order
is the order in which two switching-setup packets generated by the
switching-setup-packet generator 14 arrive at the communication
terminal 20. The second arrival order is the order in which two
response packets for the switching-setup packets arrive from the
communication terminal 20. That is, the switching controller 15
performs switching control on the communication path on the basis
of the bidirectional arrival orders between the communication
terminal 10 and the communication terminal 20.
The switching control performed by the switching controller 15
includes both communication of various switching-control packets
and a switching process for actually performing communication path
switching.
The communication-path monitor 16 uses, for example, a monitoring
parameter to sequentially monitor the communication condition of
the first communication path 31. The monitoring parameter includes,
for example, the value of a received signal strength indication
(RSSI), the value of a signal-to-noise ratio (S/N ratio), or the
value of actual throughput at the application level. The
communication-path monitor 16 monitors an increase/decrease in the
value of the monitoring parameter. In the present embodiment, a
monitoring method is not particularly limited.
The communication terminal 20 includes a third communicator 21, a
fourth communicator 22, a switching controller 23, and a
switching-control-packet generator 24.
The third communicator 21 communicates data with the communication
terminal 10 through the first communication path 31. The fourth
communicator 22 communicates data with the communication terminal
10 through the second communication path 32.
The switching-control-packet generator 24 generates a
switching-control packet for switching the communication path from
the first communication path 31 to the second communication path 32
or from the second communication path 32 to the first communication
path 31.
The switching of the communication path from the first
communication path 31 to the second communication path 32
corresponds to switching of the communicator from the third
communicator 21 to the fourth communicator 22. The switching of the
communication path from the second communication path 32 to the
first communication path 31 corresponds to switching of the
communicator from the fourth communicator 22 to the third
communicator 21. The switching controller 23 handles protocols
including, for example, FST.
In response to the switching-setup packet and the switching
confirmation packet received through the first communication path
31 or the second communication path 32, the switching controller 23
transmits a normal response (reception success) or a reject
response (reception failure) in accordance with a reception state
at the communication terminal 20.
Next, a description will be given of example operations of the
communication terminals 10 and 20.
FIG. 2 is a flowchart illustrating an example operation of the
communication terminal 10. FIG. 2 illustrates communication path
switching from the first communication path 31 to the second
communication path 32 during data communication between the
communication terminal 10 and the communication terminal 20 through
the first communication path 31.
First, for example, by using the monitoring parameter, the
communication-path monitor 16 determines whether or not the
communication condition of the first communication path 31 is bad
(S11). The "bad communication condition" as used herein refers to a
state in which it is determined that the throughput of the first
communication path 31 has decreased to a level that is lower than
the throughput of the second communication path 32.
In response to a determination indicating that the communication
condition of the first communication path 31 is bad, the
switching-setup-packet generator 14 generates a switching-setup
packet, and the switching controller 15 uses FST to transmit the
generated switching-setup packet through the first communication
path 31 (S12). The switching-setup packet includes, for example, an
FST Setup Request frame.
In response to the determination indicating that the communication
condition of the first communication path 31 is bad, the
switching-setup-packet generator 14 generates a switching-setup
packet, and the switching controller 15 uses OCT to transmit the
switching-setup packet through the second communication path 32
(S13). The switching-setup packet includes, for example, an
OCT-Channel Tunnel Request frame.
The first communicator 11 or the second communicator 12 receives,
from the communication terminal 20 through the first communication
path 31 or the second communication path 32, a response packet for
the switching-setup packet and reports the response packet to the
switching controller 15 (S14). The response packet includes, for
example, an FST Setup Response frame.
The switching controller 15 determines whether a response packet
reported earlier is a packet received through the first
communication path 31 or a packet received through the second
communication path 32 (S15). The response packet reported earlier
does not always indicate a normal response, and a response packet
reported later may indicate a normal response.
Upon determining in step S15 that the response packet reported
earlier is a packet received through the first communication path
31, the switching controller 15 determines whether the response
packet indicates a normal response or a reject response (S16).
The communication terminal 20 transmits a normal response to the
communication path 31 or 32 through which the switching-setup
packet arrived at the communication terminal 20 earlier. For
example, when the response packet received through the first
communication path 31 indicates a normal response, this means that
the switching-setup packet transmitted from the communication
terminal 10 to the communication terminal 20 (in a forward path)
through the first communication path 31 arrived earlier. Also, when
the response packet received through the second communication path
32 indicates a normal response, this means that the switching-setup
packet transmitted from the communication terminal 10 to the
communication terminal 20 (in the forward path) through the second
communication path 32 arrived earlier. That is, a normal response
is issued for the communication path through which the
communication terminal 20 has received the switching-setup packet
earlier.
The communication terminal 20 transmits a reject response to the
communication path through which the switching-setup packet arrived
at the communication terminal 20 later. For example, when the
response packet received through the first communication path 31
indicates a reject response, this means that the switching-setup
packet transmitted from the communication terminal 10 to the
communication terminal 20 (in the forward path) through the first
communication path 31 arrived later. When the response packet
received through the second communication path 32 indicates a
reject response, this means that the switching-setup packet
transmitted from the communication terminal 10 to the communication
terminal 20 (in the forward path) through the second communication
path 32 arrived later. That is, a reject response is issued for the
communication path through which the communication terminal 20 has
received the switching-setup packet later.
Upon determining in step S16 that the response packet received
through the first communication path indicates a normal response,
the switching controller 15 continues the switching control in
response to the response packet, i.e., the normal response received
through the first communication path 31 (S18).
In the switching control in step S18, for example, the switching
controller 15 switches (performs a switching process for
switching), in the communication terminal 10, the communicator from
the first communicator 11 to the second communicator 12. Also, in
the switching control in step S18, for example, the switching
controller 15 transmits a switching confirmation packet generated
by the switching-control-packet generator 13 to the communication
terminal 20 through the second communication path 32, waits for an
acknowledgement response packet for the switching confirmation
packet, and completes the communication path switching. The
switching confirmation packet includes, for example, an FST Ack
Request frame.
The switching controller 15 omits the switching control in response
to a response packet that serves as a reject response and that
arrives through the second communication path 32, subsequent to the
normal response received through the first communication path 31
(S19). This is because the normal response has already been
received from the communication terminal 20.
In a first control pattern involving steps S15, S16, and S18, the
switching-setup packet transmitted from the communication terminal
10 through the first communication path 31 arrives at the
communication terminal 20 earlier, and the switching-setup packet
transmitted from the communication terminal 10 through the second
communication path 32 arrives at the communication terminal 20
later. Also, the communication terminal 10 receives the response
packet through the first communication path 31 earlier and receives
the response packet through the second communication path 32
later.
That is, in the first control pattern, a communication through the
first communication path 31 is reported earlier in both the
transmission of the switching-setup packet by the communication
terminal 10 and the reception of the response packet from the
communication terminal 20.
Next, upon determining in step S16 that the response packet
received through the first communication path indicates a reject
response, the switching controller 15 omits the switching control
in response to the reported response packet, that is, the reject
response received through the first communication path 31 (S20).
The switching controller 15 continues the switching control in
response to a normal response that arrives through the second
communication path 32, subsequent to the reject response received
through the first communication path 31 (S21).
This is because the switching-control packet transmitted from the
communication terminal 10 (in the forward path) through the second
communication path 32 is reported to the communication terminal 20
earlier.
In the switching control in step S21, for example, the switching
controller 15 switches (performs a switching process for
switching), in the communication terminal 10, the communicator from
the first communicator 11 to the second communicator 12. Also, in
the switching control in step S21, for example, the switching
controller 15 transmits a switching confirmation packet generated
by the switching-control-packet generator 13 to the communication
terminal 20 through the second communication path 32, waits for an
acknowledgement response packet for the switching confirmation
packet, and completes the communication path switching.
In a second control pattern involving steps S15, S16, and S20, the
switching-setup packet transmitted from the communication terminal
10 through the second communication path 32 arrives at the
communication terminal 20 earlier, and the switching-setup packet
transmitted from the communication terminal 10 through the first
communication path 31 arrives at the communication terminal 20
later. Also, the communication terminal 10 receives the response
packet through the first communication path 31 earlier and receives
the response packet through the second communication path 32
later.
That is, in the second control pattern, in the transmission (in the
forward path) of the switching-setup packet by the communication
terminal 10, a communication through the second communication path
32 is reported earlier, and in the reception (in a return path) of
the response packet from the communication terminal 20, a
communication through the first communication path 31 is reported
earlier.
The second control pattern is executed, for example, when the
condition of the first communication path 31 becomes bad during the
transmission (in the forward path) of the switching-setup packet by
the communication terminal 20 and the condition of the first
communication path 31 is restored during the transmission (in the
return path) of the response packet by the communication terminal
10.
In step S21, subsequent to the reject response received through the
first communication path 31, the switching controller 15 may
suspend the switching control in response to the normal response
received through the second communication path 32. Since the
communication path is not switched from the first communication
path 31 to the second communication path 32, it is possible to
continue a high-speed communication through the first communication
path 31 whose condition has been restored.
Next, upon determining in step S15 that the response packet
reported earlier is a packet received through the second
communication path 32, the switching controller 15 determines
whether the response packet indicates a normal response or a reject
response (S17).
Upon determining in step S17 that the response packet reported
earlier indicates a normal response, the switching controller 15
continues the switching control in response to the response packet,
that is, the normal response received through the second
communication path 32 (S22). That is, in the third control pattern,
a communication through the second communication path 32 is
reported earlier in both the transmission (in the forward path) of
the switching-setup packet by the communication terminal 10 and the
reception (in the return path) of the response packet from the
communication terminal 20.
In the switching control in step S22, for example, the switching
controller 15 switches (performs a switching process for
switching), in the communication terminal 10, the communicator from
the first communicator 11 to the second communicator 12. Also, in
the switching control in step S22, for example, the switching
controller 15 transmits a switching confirmation packet generated
by the switching-control-packet generator 13 to the communication
terminal 20 through the second communication path 32, waits for an
acknowledgement response packet for the switching confirmation
packet, and completes the communication path switching.
The switching controller 15 transmits a session-disconnect packet
to the communication terminal 20 through the first communication
path 31 to suspend the communication path switching currently being
performed through the first communication path 31 (S23). The
session-disconnect packet includes, for example, an FST TearDown
Request frame.
The process in step S23 may also be omitted. When the process in
step S23 is omitted, a session through the first communication path
31 is disconnected because of timeout after a predetermined time
passes. By performing the process in step S23, the communication
terminal 10 can quickly switch the communication path to the second
communication path 32 to allow stable communication.
In the third control pattern involving steps S15, S17, and S22, the
switching-setup packet transmitted from the communication terminal
10 through the second communication path 32 arrives at the
communication terminal 20 earlier, and the switching-setup packet
transmitted from the communication terminal 10 through the first
communication path 31 arrives at the communication terminal 20
later. Also, the communication terminal 10 receives the response
packet through the second communication path 32 earlier.
The third control pattern is executed, for example, when the
condition of the first communication path 31 becomes bad during the
transmission of the switching-setup packet from the communication
terminal 10 to the communication terminal 20 (in the forward path)
through the first communication path 31 and is not restored until
the transmission of the response packet from the communication
terminal 20 to the communication terminal 10 (in the return path)
through the first communication path 31.
Next, upon determining in step S17 that the response packet
reported earlier indicates a reject response, the switching
controller 15 transmits a session-disconnect packet generated by
the switching-control-packet generator 13 to the communication
terminal 20 through the first communication path 31 to thereby
suspend to switch the communication path through the first
communication path 31 (S24).
Since the reject response transmitted through the second
communication path 32 was reported earlier, the communication
terminal 10 determines that the communication through the first
communication path 31 is active but is in a state in which the
possibility that a normal response through the first communication
path 31 does not arrive is high. Thus, the communication terminal
10 suspends the communication made through the first communication
path 31 and re-transmits the switching-setup packet through the
second communication path 32 (S25).
The communication terminal 10 may also re-transmit the
switching-setup packet through the second communication path 32
after waiting for a normal response through the first communication
path 31 for a predetermined amount of time. When the normal
response through the first communication path 31 is reported in the
predetermined amount of time, the switching controller 15 continues
the switching control through the first communication path 31
(S25).
Also, the switching controller 15 may re-transmit the
switching-setup packet to the communication terminal 20 through the
second communication path 32 by using OCT, wait for a normal
response to the switching-setup packet, and continue the switching
control (S25). When a reject response is returned in response to
the re-transmitted switching-setup packet, the switching controller
15 repeats the transmission of the session-disconnect packet
through the first communication path 31 and the transmission of the
switching-setup packet through the second communication path 32 by
using OCT until a normal response is returned.
In a fourth control pattern involving steps S15, S17, and S24, the
switching-setup packet transmitted from the communication terminal
10 through the first communication path 31 arrives at the
communication terminal 20 earlier, and the switching-setup packet
transmitted from the communication terminal 10 through the second
communication path 32 arrives at the communication terminal 20
later. The communication terminal 10 also receives the response
packet through the second communication path 32 earlier.
That is, in the fourth control pattern, in the transmission (in the
forward path) of the switching-setup packet by the communication
terminal 10, a communication through the first communication path
31 is reported earlier, and in the reception (in the return path)
of the response packet from the communication terminal 20, a
communication through the second communication path 32 is reported
earlier.
The fourth control pattern is executed, for example, when the first
communication path 31 is in good condition during the transmission
of the switching-setup packet from the communication terminal 10 to
the communication terminal 20 (in the forward path) and the first
communication path 31 during the transmission of the response
packet from the communication terminal 20 to the communication
terminal 10 (in the return path) is in bad condition.
According to the example operation illustrated in FIG. 2, since
desired switching processes are performed based on the order in
which the switching-setup packets arrive at the communication
terminal 20 and the order in which the response packets arrive at
the communication terminal 10, it is possible to improve the
accuracy of switching between the first communication path 31 and
the second communication path 32.
FIG. 3 is a flowchart illustrating an operation example of the
communication terminal 20. FIG. 3 illustrates switching of the
communication path from the first communication path 31 to the
second communication path 32 during data communication between the
communication terminal 20 and the communication terminal 10 through
the first communication path 31.
First, the third communicator 21 receives a switching-setup packet
from the communication terminal 10 through the first communication
path 31, or the fourth communicator 22 receives a switching-setup
packet from the communication terminal 10 through the second
communication path 32 (S31). The switching-setup packet includes,
for example, an FST Setup Request frame.
The switching controller 23 determines whether the switching-setup
packet is a packet received through the first communication path 31
or a packet received through the second communication path 32
(S32).
Upon determining in step S32 that the switching-setup packet is a
packet received through the first communication path 31, the
switching controller 23 transmits a normal response as a response
packet for the switching-setup packet through the first
communication path 31 and continues the switching control (S33).
The response packet includes, for example, an FST Setup Response
frame and is generated by the switching-control-packet generator
24.
In the switching control in step S33, the switching controller 23
switches (performs a switching process for switching), in the
communication terminal 20, the communicator from the third
communicator 21 to the fourth communicator 22. In the switching
control in step S33, the switching controller 23 transmits an
acknowledgement response packet for the switching confirmation
packet received from the communication terminal 10 through the
second communication path 32 and completes the communication path
switching. The acknowledgement response packet includes an FST Ack
Response frame and is generated by the switching-control-packet
generator 24.
Since the switching controller 23 receives a switching-setup packet
through the second communication path 32 after receiving the packet
through the first communication path 31, the switching controller
23 transmits a reject response as a response packet for the
switching-setup packet (S34).
Upon determining in step S32 that the switching-setup packet is a
packet received through the second communication path 32, the
switching controller 23 transmits a response packet for the
switching-setup packet through the second communication path 32 by
using OCT and continues the switching control (S35). The response
packet includes, for example, an OCT-Channel Tunnel Request frame
and is generated by the switching-control-packet generator 24.
In the switching control in step S35, for example, the switching
controller 23 switches (performs a switching process for
switching), in the communication terminal 20, the communicator from
the third communicator 21 to the fourth communicator 22. In the
switching control in step S35, the switching controller 23
transmits an acknowledgement response packet for the switching
confirmation packet received from the communication terminal 10
through the second communication path 32 and completes the
communication path switching. The acknowledgement response packet
includes, for example, an FST Ack Response frame.
Since the forth communicator 22 receives a switching-setup packet
through the first communication path 31 after the switching-setup
packet is received through the second communication path 32, the
switching controller 23 transmits a reject response, generated by
the switching-control-packet generator 24, as a response packet for
the switching-setup packet through the first communication path 31
(S36).
Next, operation examples of the communication terminals 10 and 20
illustrated in FIGS. 2 and 3 will be described as operation
examples in the corresponding control patterns for the
communication system 100.
FIG. 4 is a sequence diagram illustrating an operation example in
the first control pattern for the communication system 100. FIG. 5
is a sequence diagram illustrating an operation example in the
second control pattern for the communication system 100. FIG. 6 is
a sequence diagram illustrating an operation example in the third
control pattern for the communication system 100. FIG. 7 is a
sequence diagram illustrating an operation example in the fourth
control pattern for the communication system 100. The same steps
numbers as those in FIG. 2 are given as step numbers for the
corresponding processes in FIGS. 4 to 7.
In the third control pattern illustrated in FIG. 6, since the
communication terminal 20 receives the switching-setup packet (S12)
through the first communication path 31 later than receiving the
switching-setup packet (S13) through the second communication path
32 (S31), the switching controller 23 transmits a reject response
(S36).
The switching controller 23 does not return a response packet when
the switching-setup packet (S12) through the first communication
path 31 has not been received.
There is also the possibility that the session-disconnect packet
that the communication terminal 10 transmits in step S23 does not
arrive at the communication terminal 20, in which case, the
communication terminal 10 may disconnect the communication session
with the first communication path 31.
Since the switching controller 23 in the communication terminal 20
has received the switching-setup packet (S13) through the second
communication path 32 (S31), the switching controller 23 returns a
reject response (S36) as a response to the switching-setup packet
(S12) received through the first communication path 31, that is,
returns an invalid response. As a result, a mismatch between the
the condition of the communication terminal 10 and the condition of
the condition of the communication terminal 20 does not occur.
In the fourth pattern illustrated in FIG. 7, since the
communication terminal 20 receives the switching-setup packet (S12)
through the first communication path 31 resulting in the normal
response (S33), the switching control in the communication terminal
20 is continued. Thus, it is preferable that the communication
terminal 10 perform session disconnection (S24) to disconnect a
communication session established through the first communication
path 31.
However, since the communication condition of the first
communication path 31 is bad, whether or not the session-disconnect
packet (S24) arrives at the communication terminal 20 is
unknown.
Thus, even when the communication terminal 10 re-transmits the
switching-setup packet through the second communication path 32
(S25) because it does not receive a normal response, the
communication terminal 20 returns a reject response because it has
returned the normal response through the first communication path
31 in step S33.
Through the above-described processing, the communication terminal
10 repeats the processes in steps S24 and S25 until receiving a
normal response through the second communication path 32. The
expression "until receiving a normal response through the second
communication path 32" corresponds to, for example, a period of
time from when a communication session through the first
communication path 31 is suspended until the switching process is
started through the second communication path 32.
Thus, upon receiving the session-disconnect packet (S24) through
the first communication path 31 or not having received the
switching confirmation packet for a predetermined amount of time,
the communication terminal 20 returns to its initial state.
Accordingly, the communication terminal 20 can return a normal
response to a new switching-setup packet.
Thus, the communication terminal 10 repeats the processes in steps
S24 and S25 to thereby make it possible to receive, from the
communication terminal 20, a normal response to the switching-setup
packet.
As described above, in the communication path switching, the
communication terminal 10 sequentially transmits the
switching-setup packets to the communication terminal 20 through
the plurality of communication paths 31 and 32, and performs
switching control on the basis of the bidirectional arrival orders,
that is, the first arrival order and the second arrival order. The
first arrival order is the order in which switching-setup packets
arrive at the communication terminal 20. The second arrival order
is the order in which response (reply) packets for the
switching-setup packets arrive from the communication terminal
20.
Since the switching process through the first communication path 31
is thought to be performed at the highest speed when the switching
time is mainly taken into account, it is preferable that the
switching processes be completed using the first control pattern.
However, even with any of the second to fourth control patterns, it
is possible to execute appropriate switching processes, considering
various communication conditions of the first communication path 31
and the second communication path 32.
For example, when the communication condition of the first
communication path 31 is bad, the switching process can be
complemented through data communication through the second
communication path 32. The communication speed in the second
communication path 32 is lower than the communication speed of the
first communication path 31, however, the communication condition
of the second communication path 32 may also become bad, since it
is a path for wireless communication.
Even in such a case, it is possible to perform a switching process
through the first communication path 31.
Also, even when the communication terminal 20 does not support OCT
it can quickly perform the switching process through the first
communication path 31, since the switching-setup packets are
transmitted through the first communication path 31 and the second
communication path 32 at substantially the same time.
According to the communication system 100, the communication paths
31 and 32 can be switched between the communication terminals 10
and 20 that support FST, regardless of the condition of the
communication path from which the switching is to be performed.
Also, since the plurality of switching-setup packets are
transmitted through the communication paths 31 and 32 sequentially
(e.g., at substantially the same time), the waiting in the STT
period can be omitted, and the communication paths can be switched
at high speed. In addition, since the control pattern for the
switching control is selected in accordance with various
communication path conditions, it is possible to improve the
accuracy of switching the communication path.
Also, through use of FST, the communication terminal 10 can perform
communication, for example, by using a frequency band of 5 GHz,
even in a state in which it is difficult to perform communication
using a frequency band of 60 GHz. Additionally, through use of OCT,
the communication terminal 10 can exchange packets by using the
frequency of the communication path to which the switching is to be
performed is to be switched and can improve the accuracy of
switching the communication path.
Although a communication path for millimeter wave communication (a
band of 60 GHz) and a communication path for IEEE802.11n (a band of
5 GHz) have been described as a plurality of communication paths in
the above embodiment, it can be easily envisaged that the present
disclosure is applicable to a combination of communication paths
for which FST can be used.
Additionally, it is apparent to those skilled in the art that
various changes and modifications can be conceived within the scope
recited in the claims, and it is to be understood that such changes
and modifications also naturally belong to the technical scope of
the present disclosure.
In the embodiment described above, the description has been given
of an example in which the communication system 100 has a
configuration including one or more communication terminals 10 and
one or more communication terminals 20. The communication system
100 may have a configuration including a plurality of communication
terminals 10 and not including the communication terminal 20.
In the embodiment described above, the description has been given
of an example in which the communication terminal 10 performs a
switching process through the communication path in response to a
response returned earlier. The communication terminal 10 may also
perform a switching process by giving priority to a response
received later, for example, if a time difference between the time
at which the response is received through the first communication
path 31 and the time at which the response is received through the
second communication path 32 is within a predetermined time and a
predetermined policy is satisfied.
In the embodiment, a terminal at a receiving end (e.g., the
communication terminal 20) does not necessarily have to support FST
or OCT. Thus, it is possible to enhance the degree of freedom and
the degree of applicability for general use of the terminal at the
receiving end.
In the above embodiment, although a description has been given of
an example in which two communication paths exist between the
communication terminals 10 and 20, three or more communication
paths may exist. The number of communication paths whose
communication states are monitored by the communication-path
monitor 16 may be two or more. The communication paths to be
monitored by the communication-path monitor 16 are, for example,
communication paths in which the communication characteristics are
likely to change. Examples of the communication paths in which the
communication characteristics are likely to change include a
communication path using a millimeter wave band that has a
characteristic of traveling straight and that is susceptible to an
influence of the human body and a communication path that is used
by a large number of communication terminals and that has a low
expectation value of throughput. The switching controller 15 may
also perform control so as to select a stable communication path of
a plurality of communication paths in a stepwise manner to perform
switching.
Although the description in the above embodiment has mainly been
given of an example of the packet communication between the
communication terminals 10 and 20, the communication may also be
data communication (e.g., frame communication) other than the
packet communication.
Although the description in the above embodiment has been given of
an example in which the present disclosure is implemented by
hardware, the present disclosure may also be realized by software
in cooperation with hardware.
The functional blocks used in the description in the above
embodiment are typically realized as a large-scale integration
(LSI) circuit. The functional blocks may be individually integrated
into a single chip or at least one or all of the functional blocks
may be integrated into a single chip. The functional blocks may be
called an LSI, or may be called an integrated circuit (IC), a
system LSI, a super LSI, or an ultra LSI depending on the
difference of the degree of integration.
A scheme for integrating the functional blocks into an integrated
circuit is not a limited to a scheme used for LSI and may be
realized with a dedicated circuit or a general-purpose processor.
For example, the functional blocks can also be implemented using a
field programmable gate array (FPGA) that can be programmed after
manufacture of an LSI circuit, connections of circuit cells in an
LSI, or a reconfigurable processor that can reconfigure
settings.
In addition, when a technology for circuit integration that
replaces LSI becomes available with advancement of the
semiconductor technology or another derivative technology, such a
technology may also naturally be used to integrate the functional
blocks. For example, biotechnology is applicable to the
integration.
(Overview of Technology According to Present Disclosure)
A first communication terminal according to the present disclosure
includes:
a first communicator that communicates with another communication
apparatus through a first communication path;
a second communicator that communicates with the other
communication apparatus through a second communication path;
a communication-path monitor that monitors a condition of a
communication through the first communicator;
a switching-setup-packet generator that sequentially generates
switching-setup packets to be transmitted through the first
communicator and the second communicator, when packet loss occurs
in the communication through the first communicator; and
a switching controller that controls a switching control between
the communication through the first communicator and a
communication through the second communicator, based on a type of
which response data for the switching-setup packets arrive from the
other communication apparatus and an order in which the response
data for the switching setup packets arrive from the other
communication apparatus.
A second communication terminal according to the present disclosure
is the first communication terminal;
the first communicator communicates by using a frequency band of 60
GHz, and
the second communicator communicates by using a frequency band of
2.4 GHz or 5 GHz.
A third communication terminal according to the present disclosure
is the first or second communication terminal; and
the switching controller uses Fast Session Transfer (FST) as a
switching protocol for switching between the communication through
the first communicator and the communication through the second
communicator.
A fourth communication terminal according to the present disclosure
is the third communication terminal; and
the switching controller communicates a switching-control packet
based on the FST with the second communicator by using on-channel
tunneling (OCT).
A fifth communication terminal according to the present disclosure
is one of the first to fourth communication terminals;
the first communicator receives, from the other communication
apparatus, a first response packet for at least one of the
switching-setup packets, and when the first response packet
indicates a response for reception success, the switching
controller continues the switching control between the
communication through the first communicator and the communication
through the second communicator.
A sixth communication terminal according to the present disclosure
is the fifth communication terminal; and
when the second communicator receives, from the other communication
apparatus, a second response packet for at least one of the
switching-setup packets after receiving the first response packet,
the switching controller omits transmission control for the second
response packet.
A seventh communication terminal according to the present
disclosure is one of the first to fourth communication
terminals;
the first communicator receives, from the other communication
apparatus, a first response packet for at least one of the
switching-setup packets, and when the first response packet
indicates a reject response, the switching controller omits
transmission control for the first response packet; and
after receiving the first response packet that indicates a reject
response, the second communicator receives, from the other
communication apparatus, a second response packet for at least one
of the switching-setup packets, and when the second response packet
indicates a response for reception success, the switching
controller continues the switching control.
An eighth communication terminal according to the present
disclosure is one of the first to fourth communication
terminals;
the second communicator receives, from the other communication
apparatus, a second response packet for at least one of the
switching-setup packets, and when the second response packet
indicates a response for reception success, the switching
controller continues the switching control.
A ninth communication terminal according to the present disclosure
is the eighth communication terminal;
the first communicator transmits, to the other communication
apparatus, a session-disconnect packet for disconnecting a
communication session, and the switching controller suspends to
switch the communication through the first communicator.
A tenth communication terminal according to the present disclosure
is one of the first to fourth communication terminals;
the second communicator receives, from the other communication
apparatus, a second response packet for at least one of the
switching-setup packets; and
when the switching controller determines that the second response
packet indicates a reject response, the first communicator
transmits a session-disconnect packet, and the switching controller
suspends to switch communication through the first communicator,
and the second communicator re-transmits a switching-setup packet,
and the switching controller continues the switching control
according to a response for reception success of the re-transmitted
switching-setup packet.
A communication method according to the present disclosure is a
communication method for a communication apparatus and
includes:
communicating with another communication apparatus through a first
communicator;
communicating with the other communication apparatus through a
second communicator;
monitoring a condition of a communication through the first
communicator;
sequentially generating switching-setup packets to be transmitted
through the first communicator and the second communicator, when
the communication through the first communicator is a bad
condition; and
controlling a switching control between the communication through
the first communicator and a communication through the second
communicator, based on a type of which response data for the
switching-setup packets arrive from the other communication
apparatus and an order in which the response data for the switching
setup packets arrive from the other communication apparatus.
The present disclosure is useful for a communication terminal and a
communication method that can enhance the accuracy of switching a
communication path.
* * * * *